This invention relates to an apparatus and process for making three-dimensional objects of a predetermined shape. One useful application for such devices is rapid prototyping of models or objects. Various systems exist for such modeling purposes, including systems which build up solidifiable material deposited in layers. Such prior art systems include stereolithography and fused deposition modeling. U.S. Pat. No. 5,121,329 owned by the common assignee herewith discloses a system of the latter type which forms three-dimensional objects by depositing repeated layers of solidifying material until the desired shape is formed.
A drawback to all of the currently existing three-dimensional modeling or prototyping systems to varying degrees is their inability to produce model geometry layers in free space without a supporting layer or structure in the ultimate geometry of the final object. Objects which have overhanging segments or portions which are not directly supported in the final geometry by the modeling material require the depositing of material as a supporting structure to support the overhanging portions as the object is being built up.
In computer-driven equipment as disclosed in the aforesaid U.S. Pat. No. 5,121,329, the design of an article to be formed is initially created on a computer, with special software being utilized to provide drive signals to drive motors for a model base member and a model material-dispensing head so as to dispense material in a fluid state in such a way as to create the article of the desired shape by depositing multiple layers of material. It is possible to utilize such a system to deposit material on a base or substrate in such a way, under appropriate software control, to produce additional geometry acting as a support structure for the overhanging or free space segments of the object being formed, during the object-forming process. Anchoring the model or object geometry to such support structure solves the problem of building the model or object, but creates the additional problem of removing the supporting structure from the object structure or geometry, without causing damage to the final model or object formed. If the support structure is formed from the same material as that used for building the desired object; the strength of the bond between the support and the object is just as strong as between each individual layer of the object or model itself. When force is applied to ultimately remove the support structure from the object, either a portion of the support structure material is left on the object, or a portion of the object is torn away. In either case, the object or model is destroyed or badly scarred to the point of being worthless.
This invention is directed to a process and apparatus which overcomes the aforesaid problems by forming a weak, breakable bond between the material of the object formed and the underlying material of the support structure so as to avoid any damage to the final object.